Friday, September 29, 2017

We are now concluding five straight days of rain on the southern High Plains, but sugarcane aphids are still with us. I spent some time today collecting infested leaves and examining the aphids under a microscope, and I have to report that I can't find any evidence of the fungi that hammered populations on the Gulf Coast. (Although I will keep monitoring the situation.) Most of the aphid colonies I observed looked just fine, and there were some beneficial insects like syrphid fly and lady beetle larvae feeding on them. Dr. Katelyn Kesheimer, IPM Agent in Lubbock and Crosby counties, took 7 Day After Treatment data in a sugarcane aphid efficacy trial yesterday between rain events, and she reported that there was a slight decrease in aphid numbers on the untreated plots, but nothing to write home about.

So the rains did not really reduce the number of aphids, but, significantly, the cooler temperatures slowed them down. Aphid development and reproduction is slower in cooler temperatures, so the explosive population growth potential is not going to be here until we get significantly warmer. The practical effect of this is that fields that still require treatment, or will require treatment, do not have to be sprayed as quickly as they would be in hotter conditions. This is good for a few reasons, one of which is that it will pay to wait a few days.

We know that our insecticides do not work as well when it is cold, or, put another way, they work better when it is warm. Current predictions put the warmest days next week as Sunday - Tuesday, and then Friday - Sunday. If an application needs to be made, make it during the window of warmest days. Given that we don't really have hot weather in the forecast, it would not be a good idea to cut insecticide rates in the face of these moderate temperatures.

Dr. Kesheimer included a generic formulation of imidacloprid in her efficacy trial because growers are using it due mostly to its relatively low cost and a marketing push. We already have older data that this off-label insecticide does not provide good sugarcane aphid control, and her 7DAT data are reinforcing what we already know. Transform and Sivanto remain the effective sugarcane aphid insecticides.

Friday, September 8, 2017

Even though it is getting late in the season, sorghum is still at risk from sugarcane aphid, especially later planted sorghum. In Lubbock we are seeing leaves with thousands of aphids, and for the last two weeks many of these have been winged. These aphids have and will continue to ride the winds as they do each year. If this year is like the past three years, the aphids will spread westward and northward. Dr. Ed Bynum in Amarillo is reporting treatable populations in his area. The rains did not stop the aphids, and there is no reason to think they will stop before the first or second hard freeze. Last year we harvested sorghum at the Halfway Experiment Station after first freeze and still had plenty of aphids on the plants and in the heads.

What I am trying to say is that if you have grain or forage sorghum in the field, this is no time to get complacent.The photos below were taken at the Lubbock Research Center this morning before sunrise.

Leaves being killed by aphids, and honeydew darkening the soil where it dripped.

Leaves on late planted sorghum completely covered by honeydew from the thousands of aphids feeding on the undersides of leaves above. All of the sorghum in this field looked this way.

Mid-June planted sorghum. The untreated row is on the left, obviously. The row on the right was sprayed with 5 oz. of Sivanto.

Tuesday, August 15, 2017

After reporting yesterday of sugarcane aphids in Moore and Sherman Counties, we received an email from Stephen Cox, crop consultant. He is finding sugarcane aphids in Hansford County. We appreciate everyones help letting us know about new findings of sugarcane aphids.

Monday, August 14, 2017

I received a text today from Kaj Overstreet, crop consultant, that he has been finding sugarcane aphids in fields in Moore County. Then I received another text that he found sugarcane aphids in fields in Sherman County.

Also, last Friday, August 11th, I received a call for Mr. J. R. Sprague, County Extension Agent for Lipscomb County, that crop consultants found sugarcane aphids in a cotton field. I contact Dr. David Kerns, Texas A&M AgriLife Extension Cotton Entomologist, to determine if we should be concerned about sugarcane aphid in cotton. Besides Dr. Kerns being a cotton entomologist he worked on sugarcane aphids in sorghum while with LSU the past few years before coming back to Texas. He stated that sugarcane aphids could be found in cotton, but aphids were not able to survive to cause damage. The sugarcane aphid is indiscriminate as to where or what crops the alate (winged) aphids may land on. After a female aphid lands on a plant she will begin giving birth to live immature aphids. Since cotton is not a sorghum related plant the aphids are unable to live very long. Therefore, sugarcane aphids should not be a threat to cotton, but other aphids do live and reproduce on cotton.

Wednesday, August 9, 2017

After first being detected in neighboring Tom Green County nearly 7 weeks ago, SCA has now finally shown up in both Glasscock and Reagan Counties. The timing is quite nice as most all of the sorghum in Glasscock, Reagan and Upton Counties is drying down and anywhere from days to a week or so away from harvest. There is a little late planted grain sorghum as well as haygrazer that will have to contend with the aphid, but for the most part St. Lawrence area sorghum will be harvested before economic damage can be inflicted on the crop.

Thursday, August 3, 2017

The reports from downstate that discussed the relatively wimpy punch of sugarcane aphid this year, and the association of rain with that lack of punch, gave us hope that this week's rains on the High Plains would have the same effect. Unfortunately, I have to report that we have seen no evidence that the rainfall slowed down the aphids.

We have been monitoring several fields in Crosby and Lubbock counties for some time, and this week the aphid numbers are higher than last week - considerably higher in some places. At the Lubbock Research and Extension Center where we have had almost 2 inches of rain in a week over two events, the aphids have now exceeded the treatment threshold on pre-boot through soft dough sorghum.

There is still a chance that rain and high humidity will kick off the fungi that kill sugarcane aphids, but as yet there is no evidence this is happening. Even with the more humid days we have experienced of late, our average humidity is well below that in South Texas where the fungi were given credit for reducing aphid numbers.

The good news is that there are relatively fewer aphids coming in now than in past years, so fields are building toward treatment thresholds in a softer manner. The larger colonies on High Plains plants are beginning to generate winged aphids.

Brent Bean, Agronomist for Sorghum Checkoff, reported sugarcane aphids on sorghum in Parmer County today. Deaf Smith County was also added to the map today. DeBaca County in east central New Mexico also has confirmed sugarcane aphids. The official map has been updated to reflect these discoveries.

Friday, July 28, 2017

The crop consultant, Mr. Jess McGee, that found sugarcane aphids in a field in Donley County has now found sugarcane aphids in a field in Gray County. Also, Dr. Brent Bean, Director of Agronomy for the United Sorghum Checkoff Program, has been stopping and looking for sugarcane aphids while driving across the Texas High Plains today. He was unable to find any sugarcane aphids in any of the fields, except one forage sorghum field that was west of Canyon in Randall County. He only found one single colony after scouting the field for 30 minutes. Sugarcane aphids numbers are not very high in any of the report fields, but be these findings indicate any grain or forage sorghum field should be closely scouted for the presence of sugarcane aphids. If you discover sugarcane aphids in a field, please contact any of the individuals listed on this site that are contributors for the Texas High Plains.

Tuesday, July 25, 2017

Greg Cronholm, Independent Crop Consultant and retired Extension IPM Agent, just called to report finding sugarcane aphid in Hale County about 3 miles from Plainview. Most were small colonies but some were a bit bigger. Similar to what we saw with the early infestations in Crosby County last week, he said his colonies were in the upper ½ of the plant. For the southern High Plains we now have sugarcane aphid confirmed in Crosby, Lubbock, Hale and Floyd counties.

Sugarcane aphid is just beginning to build in fields in select counties on the Southern High Plains, and as of this writing I know of no fields that have required treatment. The sugarcane aphid distribution map can be found here. So far the aphids are building fairly slowly. This article is posted in the Sugarcane Aphid News site because sugarcane aphids should be considered if headworm control becomes necessary.

The less than good news is that fairly high numbers of headworms (corn earworm + fall armyworm) are being found in panicles. I was in a field in northeastern Crosby county last week that had 1-3 medium to large worms per head, and this field was later treated. Katelyn Kesheimer, IPM Agent in Lubbock and Crosby counties, just reported a field near Shallowater in Lubbock County that had a large number of worms. Stan Carroll, the Research Technician who runs the cotton bollworm/corn earworm traps at the Lubbock Center, told me this morning that he emptied the traps Tuesday night and had a high number of moths in them when he checked them Wednesday morning. We are therefore experiencing a big flight of cotton bollworms/corn earworms. The good news, if you can call it that, is that the fall armyworm trap captures are still well below average.

Insecticide selection for headworms is complicated now that we have sugarcane aphid or the threat of sugarcane aphid in the system. Most of our older insecticides like pyrethroids, Sevin, Lannate etc. will provide control, but they will also eliminate the beneficial insects from the field and leave it more open to damage by the sugarcane aphid. Newer insecticides like Blackhawk and Prevathon will preserve the beneficial insects, but they are more expensive than the older products. Besiege is a combination product; it has the same active ingredient as Prevathon but with a pyrethroid as well. Besiege will not preserve beneficial insects. If a headworm treatment is needed then the risk of sugarcane aphid will have to be factored into the choice of insecticides. As an additional complication, we think our corn earworm is still susceptible to pyrethroids in spite of some slippage downstate, but we know that fall armyworm is less susceptible to pyrethroids, especially the larger worms. One good thing is that headworms do not require the high gallons per acre of spray that sugarcane aphids do, so applications can be made with 3-5 GPA - but check the label for the specific product you intend to use.

Treatment thresholds are based on the size of the worms, number of worms per acre, heads per acre, control cost and value of the crop. For example, in the table below a treatment would be justified at 14,000 large worms (longer than 1/2 inch) per acre when the cost of control was $10/acre and the grain value was $7.00/cwt. To put this in perspective, if the field had 28,000 plants per acre, this would be one large worm per two plants. The online headworm threshold calculator is here.

Friday, July 21, 2017

Dr. Katelyn Kesheimer, IPM Agent in Lubbock and Crosby counties, sent the following notification last night. Given the recent aphid discoveries in nearby Floyd county, and a new discovery this week in Lubbock County, it seems like the annual aphid incursion has begun, albeit at a slower pace than in years past.

"Yesterday I was in a field in northeastern Crosby County that had building populations of sugarcane aphids. It is in the same area that we first found aphids last year as they trickled in from the east and slowly moved west.

SCA colonies were a couple hundred at most and only on a few plants. I’ve attached a picture of one of the colonies – it's mixed with adults, nymphs, and you can see the alates (winged aphids) starting to form. There was also honeydew on some leaves. Yellow sugarcane aphids were in the field as well and populations were starting to build. The field is at soft dough.

We didn’t have a lot of sorghum in our area at the beginning of the season, but with replants the last month there is quite a bit of young sorghum in addition to the acres that are already blooming."

Thursday, July 20, 2017

Yesterday, Brent Bean received a call from Justin McGee, Independent Agronomist, that he had found sugarcane aphids in a field that is located in the very Northwest corner of Donley County. Justin sent me the gps coordinates to the field and I went today, July 20th, and I too found the aphids. I did not doubt Justin’s finding, but I wanted to see for myself before sending out a newsletter with the bad news. From what I found there were very few winged and non winged aphids, one to 4 aphids on a single leaf on a plant, and the percentage of plants infested were less than 10%.

Also, yesterday afternoon Blayne Reed posted to his blog that sugarcane aphids were found in Floyd County by Clay Golden, Independent Crop Consultant, https://halecountyipm.blogspot.com/2017/07/sugarcane-aphid-arrives-in-floyd-county.html. The field was located in Southwestern Floyd County near the community of McCoy. We can hope the sugarcane aphids will be just as slow to build up in the Panhandle as they have been in Lubbock County and in Tom Green County. However, with these findings, scouting for SCAs will, unfortunately, need to be intensified across the Panhandle and the Central Plains.

If you do find sugarcane aphids, please send samples or photos of the aphids to your County Extension Agent, IPM Extension Agent or to Dr. Pat Porter or me, Ed Bynum. This will allow us to better inform everyone where the sugarcane are and the movement of the aphids. We greatly appreciate Justin McGee and Clay Golden for telling us what they found so we can now keep you informed about the movement and activity of the sugarcane aphid.

Sunday, June 25, 2017

SCA have been confirmed in sorghum in southern Lubbock County, making this the farthest north in Texas that the aphids have been found in 2017. Only small colonies have been found so far, but now is the time to intensify scouting efforts.

Friday, June 23, 2017

This is the second article meant to help prepare
for sugarcane aphid arrival on High Plains sorghum in 2017. The first article is here.

Our High Plains economic thresholds are valid

The treatment thresholds in place at the start of
2016 proved to be effective in preventing economic losses when insecticides
were applied in a timely manner with good coverage at the appropriate rate.
These thresholds were adopted from work originally done at LSU and reflect a
higher damage potential the earlier in plant development that the aphids exceed
threshold.

Black layer*: Heavy
honeydew and established aphid colonies with treatment only for preventing
harvest problems.

(* Thresholds that are used successfully in
the field but have not yet been validated by research.)

Control is effective if coverage is optimal, solid
rates are used, and beneficials are protected

On-farm control of SCA was often achieved in 2016
thanks primarily to prompt application at threshold and a willingness to use solid
rates of insecticide with plenty of carrier volume to achieve at least 5 GPA by aerial application or 15 GPA by ground application. Many of the
control failures could be traced back to lack of coverage, rate, or letting the
aphids become too numerous before applying insecticide.

Another major source of
SCA control failure involved elimination of beneficial insects. In some cases
this was done by tank mixing a hard insecticide like a pyrethroid,
Lorsban or Dimethoate with either Transform or Sivanto, the two dedicated and
effective aphid insecticides which were usually present in the tank at lower
rates than if they had been used alone. These hard insecticides killed the
beneficial insects and allowed a quick resurgence of aphids in the field. The
use of hard insecticides for other non-SCA pests like headworms or midge also
resulted in a SCA resurgence.

Dr. Ed Bynum conducted a 2016 insecticide efficacy
trial at Bushland with Transform, Sivanto and two non-labeled insecticides. In
this trial he had excellent spray coverage from a backpack sprayer, a situation
not likely to be encountered in a commercial application but which allowed direct
comparison of insecticides when coverage was not an issue.

The two registered SCA insecticides, Transform and
Sivanto, provided equivalent initial control of the aphid. Residual control
with Transform began to wane after eight days. The extreme rebound of aphids in
the Transform plots is likely due in part to this being a small plot
experiment; there were many aphids on nearby untreated plants that could infest
the Transform plots after residual activity ended.

There is some discussion of whether Transform and
Sivanto can be applied at less than 1.5 and 5.0 oz., respectively. Of course
they can, and if the application is made at threshold and not too late,
coverage is good and it is not too cold, then good control could be expected.
However, using a lower rate reduces the margin for error, the buffer against
things being less than perfect. For that reason we are still going to suggest
that 1.5 oz. of Transform and 5.0 oz. of Sivanto are the best rates for aerial
application.

Yield losses if control is not achieved

In several of our 2016 research trials we had SCA
build to high numbers at and after flowering and we lost almost 100% of the
yield (not including subsequent lodging). Experience has taught us that High
Plains SCA are capable of more damage at later growth stages than elsewhere in
the country. The reason(s) for higher potential damage on the High Plains
are unclear, but our data from Lubbock, Halfway and Bushland suggest that
sorghum grown under moderate drought stress may be more prone to yield loss
than a more fully irrigated crop.

We conducted three experiments in 2016 that
resulted in different amounts of leaf damage in plots. These experiments either
had aphid numbers intentionally manipulated by various timings of different
insecticides (Lubbock), or they were the result of different insecticide
efficacy in our control trials (Halfway and Bushland). At various times after
flowering we rated leaf damage on a 0 - 10 scale. Zero indicates no aphid
damage. A damage rating of 1 indicates the lower 10% of the canopy has damaged
leaves. A rating of 5 indicates the lower 50% of the canopy has leaf damage,
and a rating of 10 indicates that all of the leaves are damaged. We harvested
the plots, threshed the panicles and determined yield adjusted to 15.5%
moisture. Yields were then regressed against the leaf damage rating taken at
harvest.

Both Lubbock and Bushland experiments were
conducted on sugarcane aphid susceptible sorghum grown under furrow irrigation.
The Lubbock trial was pre-watered and received two supplemental irrigations
during the season. The Bushland trial was pre-watered and then rain-fed for the
rest of the season, and there was not much rain before early September.

Yield vs. Damage Rating at Lubbock, 2016, Kesheimer
and Porter.

The Lubbock experiment lost 317 pounds of yield for
each additional level of leaf damage incurred. For example, if the plants had
been re-treated to stop aphid activity at a leaf damage rating of 2, the yield
would have been approximately 4,700 lbs. per acre. However, if the aphids were
not controlled until they caused a leaf damage rating of 7, the final yield would have been only 3,115 pounds. (5 more levels of leaf damage x 317
pounds/damage rating = -1,585 lbs. of additional yield loss, or a yield of
4,700 - 1,585 = 3,115 pounds.)

Yield reduction at Ed Bynum's experiment in
Bushland was 409 lbs. per additional level of leaf damage rating. The Bushland
field was less well irrigated than the Lubbock field.

Our third experiment, conducted by Blayne Reed at
Halfway, used a "resistant" sorghum hybrid grown under abundant drip
irrigation. In this case yield loss was only 155 lbs. per additional level of
leaf damage rating, but whether this lower yield loss is due to abundant
irrigation, a "resistant" hybrid, or some interaction of the two
factors is unclear.

Second application treatment threshold

It is not economically feasible to make follow-on
insecticide applications at the relatively low first application threshold, but
our 2015 and 2016 data strongly suggest that a second application should be
timed in order to protect the top 50 - 60% of the canopy. This second
application should be made as quickly as possible; Ed Bynum's 2016 Bushland
experiment went from an average leaf damage rating of 3 to an average of 6 in
just 5 days.

Search This Newsletter

The information given herein is for educational purposes only. References to commercial products or trade names are made with the understanding that no discrimination is intended and no endorsement by Texas A&M AgriLife Extension is implied.

We do not mind if others use the information in Texas Sugarcane Aphid News for their own purposes, but please give the appropriate credit to Texas Sugarcane Aphid News when you do. Images may or may not be copyrighted by the photographer or an institution. They may not be reproduced without permission. Contact the author of a post to determine the copyright status of images.